The U.S. Attorney's Office in Raleigh issued a grand jury subpoena demanding records from the North Carolina Department of Environment and Natural Resources.

RALEIGH, N.C. -- Federal authorities have launched a criminal investigation into a massive coal ash spill into the Dan River. The U.S. Attorney's Office in Raleigh issued a grand jury subpoenas demanding records from Duke Energy and the North Carolina Department of Environment and Natural Resources.

The subpoenas seek emails, memos and reports from 2010 through the Feb. 2 spill. The Associated Press obtained a copy on Thursday of the subpoena issued to the state. A Duke spokesman confirmed the company had also received one. The spill at a Duke Energy plant in Eden spewed enough toxic sludge into the river to fill 73 Olympic-sized pools.

It was the third-largest coal ash spill in U.S. history. Prosecutors ordered the state environmental agency's chief lawyer to appear next month before a grand jury.